Realm and Lessons Learned building it

{MBLT}DEV ‘14

Brian Munkholm, VP Engineering @realm bm@realm.io @brianMunkholm

Menu:What is Realm? How popular? Why use Realm? Feedback Design goals & fulfilment - API examples Lessons Learned The future

What is Realm? • Modern mobile database - replace SQLite+ORMs • Easy: Object-oriented, but not an ORM • Safe: full ACID properties • Cross-platform: C++ core (3 years dev) • Small: compact data, object == DB (no copy!) • Fast • Free: open source!

Realm for iOS Used by >20,000 developers worldwide in < 8 weeks!

Including ~1,000 in or very close to production

>2200 GitHub Stars!

(Parse: 10k in 8 mon)

Realm for Android - launched 1 month ago Used by >5,000 developers worldwide the 1’st week!

First apps in production

>700 GitHub Stars in 2 weeks (GreenDao has 1592, ORMlite 307 after years!)

Why use Realm? - ask the devs!

http://www.allgenxyz.com/wp-content/uploads/2013/10/rocket-snail_1252621_GIFSoup.com_.gif

Cloth

a beautifully designed personal outfit diary

>350k users

Uses Realm for all data handling

took over a 2 year-old codebase and ported it to Realm in 1 day.

clothapp.com reallyseth.com

Beanflow

Full POS & inventory app (w/ offline mode)

Uses Realm as network cache for all data

“I don't have any plans to go back to Core Data anytime soon. I really like Realm.”

sebastiandobrincu.com www.beanflow.com

Common benefits • Save time - save $$$ • Make faster & better apps • Uses less memory and disk • Free (de)serialisation • cross platform (iOS, Android, ++) • cross language

Design Goals

1. Simple

2. Fast 3. Modern

to learnto maintainto use across threads

1. Simple

public class Dog extends RealmObject { // Fields private String name; private int age; // + Getters and Setters… }

Models

// Obtain a Realm instance in each thread Realm realm = Realm.getInstance(this);

// ACID transactions give you easy thread-safety realm.beginTransaction();

Dog dog = realm.createObject(Dog.class); dog.setName("Rex"); dog.setAge(3);

// Full commit to disk (or memory) realm.commitTransaction();

Writes

RealmResults<User> teens = realm.where(User.class) .between("age", 13, 20) .findAll();

Queries

// Queries can be chained efficiently RealmResults<User> johns = teens.where() .equalTo("name", “John") .or() .contains("name", “Jo") .findAll();

public class Person extends RealmObject { private String name; private Dog bestDog; // One-One relations private RealmList<Dog> dogs; // One-Many relations … } realm.beginTransaction();

Person person = realm.createObject(Person.class); person.setName("Tim"); person.getDogs().add(dog);

realm.commitTransaction();

Relationships

new AsyncTask<Void, Void, String>() { @Override protected String doInBackground(Void… voids) {

Realm realm = Realm.getInstance(this); realm.beginTransaction(); Person person = realm.createObject(Person.class); person.setName("Tim"); realm.commitTransaction();

return null; } }.execute();

Thread-safety: All access is the same

• Writes cannot conflict - they block

• No need to merge data sources, ever.

• Reads are consistent as soon as the write completes

Thread-safety:

2. Fast

BIG disclaimer! Use benchmarks as rough indicator Measure your own senarios

Lessons Learned

Lesson one

Aim high! • Worlds best product • Solid funding from the best • 100% dedicated team

Lesson two

Listen to the users / community • Ask users actively • Listen, understand their needs

and react quickly • It takes time!

Lesson three

Performance is great - but usability is king! • and eats performance… • Android/Java reflection is SLOW • but dont’ give up

Add a new object first time

• Runtime code generation • Use lower level APIs • Compile-time code

generation • Cache all the introspection

calls

0

25

50

75

100

Runtime Runtime+ Compile Time Cache

4 sec!!!

The future: • Encryption • Handover results between threads • Dynamic API / Migration • Advanced Query • Synchronisation • What do you want for xmas?

Watch or Influence?

Feedback : realm.io bm@realm.io #Realm #BrianMunkholm

Thanks for your support!!!